Key Technology Introduced in Hyper-V

The beta release of the update to Windows Server 2008 will be of special interest to those who work with virtualization, as it unveils a key technology long-promised by Microsoft.

A blog on Microsoft's TechNet Website
announced earlier this week that the "R2" beta version of Windows 2008 includes significant upgrades to Hyper-V, Microsoft's proprietary hypervisor. The most crucial of these is the introduction of "Live Migration," which allows virtual machines (VMs) to be moved from one physical server to another with no downtime or loss of connectivity.

Hyper-V originally shipped with "Quick Migration," which migrated running VMs with a short interruption. The interruption, however, did involve temporarily shutting down the VM, which can result in dropped connections and loss of system state data.

Live migration was originally supposed be part of the original Hyper-V release, code-named "Viridian" at that time, but it was delayed so that Microsoft could hit its shipping date. Hyper-V came out last June, and at that time Microsoft stated that the R2 release of Windows 2008 would include Live Migration in Hyper-V.

Hyper-V is included as part of Windows 2008, but also has a stand-alone version, called Hyper-V Server, that doesn't require Windows. It also includes Live Migration.

Live Migration is essential to help Microsoft compete with virtualization industry leader VMware. Palo Alto, Calif.-based VMware has included its version of Live Migration, known as Vmotion, in its ESX hypervisor for years. Many medium and large enterprises will not consider a hypervisor without Live Migration capability, according to Burton Group Analyst Chris Wolf, who specializes in virtualization.

"It's one of the core features that most enterprises must have," Wolf said. "It gets them (Microsoft) closer to leveling the playing field with VMware." Wolf says that Live Migration, while promising, will have to scale and perform well to be considered comparable to Vmotion.

Live Migration is also offered in other products, most notably the open source Xen hypervisor. Xen is the basis for virtualization platforms from a host of companies like Citrix, Virtual Iron, Novell, Sun and others.